An MAO inhibitor that is effective in the treatment of major depression, dysthymic disorder, and atypical depression. It also is useful in the treatment of panic disorder and the phobic disorders. (From AMA, Drug Evaluations Annual, 1994, p311)

This compound belongs to the benzene and substituted derivatives. These are aromatic compounds containing at least one benzene ring.

Pharmacology

Indication

May be used to treat major depressive disorder.

Pharmacodynamics

Isocarboxazid is a non-selective hydrazine monoamine oxidase (MAO) inhibitor used to treat depression. In vivo and in vitro studies demonstrated inhibition of MAO in the brain, heart, and liver. Depression is a complicated disease that is not fully understood. It is thought that depression may be linked to an imbalance of chemicals within the brain. When depression occurs, there may be a decrease in the amount of chemicals released from nerve cells in the brain. These chemicals are called monoamines. Monoamines are broken down by a chemical called monoamine oxidase. Isocarboxazid prevents monoamine oxidase from breaking down the monoamines. This results in an increased amount of active monoamines in the brain. By increasing the amount of monoamines in the brain, the imbalance of chemicals thought to be caused by depression is altered. This helps relieve the symptoms of depression.

Mechanism of action

Isocarboxazid works by irreversibly blocking the action of a chemical substance known as monoamine oxidase (MAO) in the nervous system. MAO subtypes A and B are involved in the metabolism of serotonin and catecholamine neurotransmitters such as epinephrine, norepinephrine, and dopamine. Isocarboxazid, as a nonselective MAO inhibitor, binds irreversibly to monoamine oxidase–A (MAO-A) and monoamine oxidase–B (MAO-B). The reduced MAO activity results in an increased concentration of these neurotransmitters in storage sites throughout the central nervous system (CNS) and sympathetic nervous system. This increased availability of one or more monoamines is the basis for the antidepressant activity of MAO inhibitors.

MAO Inhibitors may enhance the hypertensive effect of Amphetamines. Concomitant use of amphetamines and monoamine oxidase inhibitors (MAOI) should be avoided. If used concomitantly, careful monitoring of blood pressure must occur. It may take up to 2 weeks after the discontinuation of an MAOI for the effects to dissipate enough to afford safety to the administration of interacting agents.

MAO Inhibitors like isocarboxazid may enhance the hypertensive effect of Alpha2-Agonists (Ophthalmic). The concomitant use of monoamine oxidase inhibitors and ophthalmic alpha2 agonists is contraindicated.

Buprenorphine may enhance the adverse/toxic effect of MAO Inhibitors like isocarboxazid. When possible, avoid use of buprenorphine in patients who have used a monoamine oxidase inhibitor within the past 14 days due to possible severe adverse effects.

The therapeutic effects of the central acetylcholinesterase inhibitor, Tacrine, and/or the anticholinergic, Isocarboxazid, may be reduced due to antagonism. The interaction may be beneficial when the anticholinergic action is a side effect. Monitor for decreased efficacy of both agents.

Tolcapone and Isocarboxazid decrease the metabolism of endogenous catecholamines. Concomitant therapy may result in increased catecholamine effects. Consider alternate therapy or use cautiously and monitor for increased catecholamine effects.

The MAO inhibitor, isocarboxazid, may increase the serum concentration of zolmitriptan by decreasing its metabolism. Concomitant therapy and use of zolmitriptan within two weeks of discontinuing isocarboxazid are contraindicated.